Portable trenching device



Oct. 9, 1962 Filed Nov. 2, 1960 W. E. GEORGE ETAL PORTABLE TRENCHINGDEVICE 6 Sheets-Sheet l INVENTORS WARREN E .GEORGE FRED C. KIECHEL GLENNW. MCININCH ATTYs Oct. 9, 1962 w. E. GEORGE ETAL 3,057,088

PORTABLE TRENCHING DEVICE 6 Sheets-Sheet 2 Filed Nov. 2, 1960 INVENTORSWARREN E.GEORGE FRED C. KIECHEL GLEN W. McINmcH M //v-/ ATws,

Oct. 9, 1962 w. E. GEORGE ETAL 3,057,088

PORTABLE TRENCHING DEVICE Filed Nov. 2, 1960 6 Sheets-Sheet 3 OUT PUTRPM o VALVE TRAVEL (CONTROL COLLAR nu) INVIENTORS WARREN E. GEOQGE FREDC. KEECHEL Grams W. W: lNmcH gf 2 W 2/4 ATTYS.

Oct. 9, 1962 w. E. GEORGE ETAL 3,05

PORTABLE TRENCHING DEVICE Filed Nov. 2, 1960 6 Sheets-Sheet 5 a 4nvmvroxs Jaw .. WARREN 56:50am;

I FRED C. KIECHEL F" Z3 GLENN WMcImNcH & b zJ/%, Wax mm rm's w. E.GEORGE ETAL 3,057,088

PORTABLE TRENCHING DEVICE Oct. 9, 1962 6 Sheets-Sheet 6 Filed Nov. 2,1960 INVENTORS WARREN E-GEORGE FRED C. KIEcHEL GLENN W. McImNcH W 26%,M, w MA TTYS 3,057,088 PORTABLE TRENCHING DEVICE Warren E. George andFred C. Kiechel, Auburn, and

Glenn W. Mclninch, Omaha, Nehr., assignors to Anburn Machine Works, Inc,Omaha, Nebr., a corporation of Nebraska Filed Nov. 2, 1960, Ser. No.66,737 14 Claims. (Cl. 37--86) The present invention relates totrenching devices and more particularly to a self-propelled trenchercapable of being maneuvered by hand into trenching position.

In the past, most commercial trenching operations have employedtrenching attachments secured to a tractor or vehicle and manuallyguided trenchers have not been favored except for the digging of shallowtrenches used to accommodate electrical conduits. Manually guidedtrenching devices capable of digging a trench of 3 to 6 inches in widthand up to, say, 4 feet in depth have been diflicult to maneuverrequiring application of brute force and difficult to transport to thedigging location.

Accordingly, it is an object of the present invention to provide amanually operated trencher which is easily maneuvered into diggingposition, convenient to operate, and readily transported from job tojob. It is a related object to provide a trencher which can readily beturned or skewed by application of light manual efiort. In short, it isan object to provide a trencher in which light manual control forces areall that is required to jockey the machine into precise diggingposition. It is an object to provide a trenching machine which is notonly easily maneuvered under manual control but which is exceedinglycompact and thus capable of use in narrow quarters not accessible by aconventional tractor or jeep-mounted trencher. It is a further object ofthe invention to provide a trencher which, although compact and easilymanuvered is nevertheless heavy duty in that it is capable of diggingtrenches of adequate width and depth for the installation of draintiles, sewer lines and the like and for domestic utilities includinggas, water and electric lines, particularly where the latter areincluded in a common trench,

It is another object to provide a trencher having a high degree oftraction and in which the weight, augmented by the suck of the diggerblades is distributed substantailly equally over two spaced pairs oftraction wheels. It is still another object to provide a trencher havinga special pair of wheels capable of being lowered to ground engagementto assume the weight of the trencher during transport or While jockeyinginto position but capable of being raised clear of the ground during theactual trenching operation. It is another object of the invention toprovide a trencher having a novel arrangement of tractive and auxiliarysupporting wheels in which the auxiliary Wheels are locatedsubstantially at the center of gravity so that when the latte-r are intheir lowered ground engaging position the trencher is balancedrequiring only light efiort to move the machine with the traction wheelsclear of the ground. It is another object to provide a trencher havingseparate sets of wheels for traction and maneuvering into position,making a total of six wheels but in which the wheels are compactlyinterfitted, with one set of the tractive wheels in an inwardatent 1yoffset position thereby to insure the advantages of easy maneuverabilityand the compact construction and appearance assoicated with use of shortwheelbase. In this connection it is an object to provide a trencherconstruction in which the effective wheelbase for maneuvering purposesis little more than one-half of that of machines of comparable size butof conventional design.

It is still another object of the invention to provide a trenchingmachine having a separate driving arrangement for maneuvering and foractual trenching operations which can be shifted from one mode ofoperation to the other simply by throwing a control lever and withoutthe necessity for inserting or removing drive pins or similar mechanicalcoupling devices. In one of its aspects it is an object of the inventionto provide a trenching machine in which power may be utilized in themaneuvering procedure but in which the supporting wheels areindependently pivoted :and free of any connection to the power source.

It is a more specific object of the invention to provide a trencherwhich includes a novel transport wheel arrangernent which enables thetrencher to be maneuvered while balanced solely on the transport wheelsbut which, nevertheless, permits power driving either forwardly orbackwardly simply by rocking the trencher in one direction or the otherto bring a selected pair of traction wheels into driving contact withthe ground.

It is an object to provide a novel slow speed driving arrangement forthe traction wheels which enables the unit, in spite of limited size,limited power of the engine, and limited weight to accomplish almost allof the work conventionally done by a trencher of the vehicle mountedtype. It is a related object to provide a trencher having a novelvariable speed hydraulic driving arrangement capable of applying apredetermined, but adjustable torque to the driving Wheels and soconstructed that upon striking a large root, heavy clay or the like, theforward motion of the trencher is temporarily slowed until theobstruction has been chewed away, following which speed is automaticallyresumed. It is a more specific object to provide a trencher havingmaximum traction at the driving wheels with the wheels locked gear-liketo the ground but in which intentional slippage takes place in thedriving connection when hard-going is encountered to limit the torqueapplied to the driving wheels to a value below that which will causewheel slippage. It is another object related to the foregoing to providedrive connection which is capable of limiting the driving torque to apredetermined, settable amount but which is nonretrograde so that thedriving wheels do not give in the opposite direction thereby preventingcyclical bucking or bounceback when diflicult digging is encountered.

It is a further detailed object to provide hydraulically powered meansfor bringing transport wheels into position to support the trencher fortransport purposes which is fail-safe and which provides for automaticlocking in transport position. This prevents the trencher from beinglowered into contact with the ground inadvertently while being towedbehind a truck or automobile at highway speed.

It is another object of the present invention to provide highwaytransport Wheels as an integral part of the trencher thereby making itunnecessary to load the trencher onto a trailer for transport from jobto job. This not only saves the inconvenience of loading or unloadingbut it is economical since it saves the expense of a trailer.

It is another object to provide a boom assembly which includes a boomhousing and a boom telescoped therein and adjustably extensible toaccommodate chains of different length and to take up for wear andelongation of the chain. In this connection it is an object to provide aboom housing which carries all of the auxiliary parts such as the auger,idler and dirt shield so that a boom of different length may besubstituted and the chain changed to one of different length quickly andeasily and without removal or adjustment of the auxiliary parts.

It is one of the detailed objects of the invention to provide in atrenching machine, having a pair of central wheels for transport, a towbar which permits adjustment for the height of the towing connection andwhich is retractable into the machine, out of the way, during thetrenching operation.

In one of its aspects it is an object of the present invention toprovide a trencher having a novel box-type body of great rigidity andstrength and which serves as a fixture for the support of connected andmoving parts in permanent alinement with one another and which enablesthe whole assembly to be made and fitted together with a precision whichis beyond that normally achieved in the field of trenching equipment. Itis a related object to provide a trencher having a box-type body providing a lower profile and smaller width than trenchers of conventionaldesign. In this connection it is an object to produce a trencher whichhas an attractive streamlined appearance and with the various operatingparts being out of sight yet with the necessary control leversconveniently accessible to the operator. It is an object to provide atrencher which is inherently strong and durable and which may beoperated for long periods of time under the most difficult operatingconditions without strain or danger of mechanical breakage.

Finally, it is an object to provide a trenching machine which providesin a novel combination the trench digging capability of a vehiclemounted trencher and ability to operate in tight quarters possessed by amanually guided trencher but which is simple in construction,inexpensive to manufacture and which requires little or no maintenanceover extended periods of use.

Other objects and advantages of the invention will become apparent uponreading the attached detailed description and upon reference to thedrawings in which:

FIGURE 1 is a perspective view of a trencher construction in accordancewith the present invention with the digger chain ready to be loweredinto the ground.

FIG. 2 is a top View of the trencher shown in FIG. 1 with the top of thehousing broken away in order to re veal the enclosed mechanism.

FIG. 3 is a side view of the chain drive connection between the engineand the digger chain.

FIG. 4 is a front view, in perspective, of the trencher with the boomhousing and bearing caps removed.

FIG. 5 is a perspective showing the boom housing and associated augerflights.

FIG. 6 is a vertical section taken through the boom housing showing themeans for adjusting the boom length.

FIG. 7 is a diagrammatic perspective showing the means for driving atractive wheel.

FIG. 8 is a diagrammatic perspective showing the means for controllingthe hydraulic coupling.

FIG. 8a shows the characteristic curves of the hydraulic coupling.

FIG. 9 is a fragmentary section taken through the trio tion positioningdevice of FIG. 8.

FIG. 10 is a top view of the forward-reverse gear box.

FIG. 11 shows the linkage associated with the transport wheels with thelatter in upraised position.

FIG. 12 is a view similar to FIG. 11 but showing the wheels in loweredtransport position and with the locking element engaged.

FIG. 13 is a diagrammatic view of the hydraulic system for operating theboom housing and transport wheels.

'FIG. 14 is a side view showing the trencher in its balanced conditionfor skewing into place by an operator.

FIG. 15 is a perspective showing the transport of the present trencherbehind an automobile.

FIG. 16 is a fragmentary section showing the hitch adjusting mechanism.

FIG. 17 is a diagram of an alternate form of transmiss1on.

While the invention has been described in connection with a preferredembodiment, it will be understood that we do not intend to be limited tothe particular embodiment shown but intend to cover the variousmodifications and equivalent constructions included within the spiritand scope of the appended claims.

Turning to the drawings and particularly to FIGURE 1, there is shown atrencher 20 constructed in accordance with the present invention. Itincludes a body 21 of hollow box-like construction supported fore and afon traction wheels 23, 24 and having a pair of transport wheels 25 towhich later reference will be made. Extending from the right-hand ortrailing end of the body is a boom assembly 30 about which is trained adigging chain 31 carrying a set of digger blades 32. Mounted on the boomassembly 30 is an auger 35 which moves the excavated dirt away from thetrench laterally in both directions. For the purpose of driving thetraction wheels 23 and the chain 31, an engine or prime mover 40 isprovided at the left-hand end of the trencher. Mechanical coupling meansemployed to drive the chain at high speed and the traction wheels atrelatively low speed will be described in connection with the otherfigures. It will suffice to say that the torque transmitted to thetraction wheels, and hence the speed under given load conditions, iscontrolled by a manual control lever 41, and the direction of movementof the trencher, whether forward or reverse and with an intermediateneutral, is under the control of a lever 42. In order to raise and lowerthe boom assembly 30, an hydraulic lift is provided under the control ofan hydraulic control lever 43. Hydraulic means are also provided forraising and lowering the transport wheels 25 under the control of alever 44.

For the purpose of maneuvering the trencher into position and also forguiding it in the desired direction of the trench, a tubular framework50 is provided at the front of the trencher including handles 51, 52 ata convenient height for the operator. And for the purpose of towing thetrencher from job to job behind a truck or automobile, a hitch,generally indicated at 55, is provided at the forward end.

With the over-all appearance of the machine in mind, it will beconvenient, in the discussion which follows, to consider in some detailthe various sub-assemblies which, either solely or jointly with othersub-assemblies, contribute to the final result and to the features andadvantages of the present machine. Thus attention may first be given tothe boom assembly 30 disclosed in FIGURES 2-6, inclusive, butparticularly well shown in FIG. 5. Here it will be noted that theassembly includes a boom housing 60 which is of hollow, elongatedconstruction and having a pair of alined supporting brackets 61, 62defining a space 63 between them. Projecting laterally from the brackets61, 62 are stub shafts or trunnions 65, 66 which are mounted in bearings67, 68 (see FIG. 4) fixed in the body 21 of the trencher.

Telescoped into the boom housing 60 is a boom 76 having an idler 71 atits outer end. The boom 70 is rigidly connected to the boom housing yetadjustable with respect to it. As shown in FIG. 6, a pin 72 projectsthrough the boom and boom housing, registering with an opening 73 in theboom and slots 74 in the housing. Since the boom is of hollowconstruction, the opening 73 is preferably reinforced with .a length ofpipe or tubing as illustrated. In order to adjust the degree ofextension of the boom and thereby take up any wear or elongation whichmay occur in the chain, the pin 72 is mounted upon threaded supports 75which are anchored in eyes 76 welded or otherwise secured to the boomhousing. Turning the nuts '77, as will be apparent, moves the pin in theslots 74 providing the necessary takeup. In order to accommodatedifferent lengths of chain for digging trenches of difierent depth,additional openings 78 are provided in the boom, reinforced in the samemanner as the opening 73, for selectively accommodating the pin 72.

In carrying out the present invention, the auger assembly which engagesthe lower run of the chain and the idler which engages the upper run ofthe chain are both secured to the boom housing so that neither of theseelements need be adjusted or disturbed when changing from one length ofboom to another. Turning next to the auger assembly 35, it includes ashaft having left and right-hand flights 91, 92, respectively, mountedon tubular supports 93, 94. The shaft 90 is supported at the center on abracket formed of a U-shaped piece of metal having edges which aresecured to the side walls of the boom housing by bolts 96. Fore and aftadjustment is provided by a series of holes 97. It is one of thefeatures of the present arrangement that the flights 91 are not fixedwith respect to the shaft 90 but are adjustable inwardly and outwardlyin order to accommodate digger blades having different width or span. Toprovide this adjustability, the tubular supports 93, 94 are providedwith a series of holes 98 which selectively register with holes in theshaft 90 and with the parts being secured together by an inserted rollpin or the like.

For the purpose of rotating the flights the auger shaft 96 has at itscenter a sprocket 100 which is alined with the chain and in mesh withit. The upper run of the chain is supported by an idler 1111 mounted ona bracket 102 which is welded or otherwise fixed to the boom housing 60.

To drive the chain, a chain drive shaft 105 is provided having a drivesprocket 106 which is centered in the space 63 between the two alinedbrackets 61, 62 of the boom housing. To provide access, the two stubshafts or trunnions 65, 66 which support the boom housing are madehollow for reception of the shaft 105, and suitable bearings areinterposed. For the purpose of coupling the engine 411 to the chaindrive shaft 105, a roller chain 110 is used (see FIG. 2) which liesadjacent the inside wall of the trencher body. At the front end, thechain 110 is trained about a sprocket 111 which projects from a gear box112 which is integral with the engine 40 and which has a control lever113 to engage and disengage the driving chain. At the rear end of thechain 110 a sprocket 115 is provided which is secured to the shaft 195and which is provided with shear pins 116 made of hard wood or the likeand designed to break when the digging chainencounters some non-yieldingobstruction in the ground. The chain 110 is kept taut by idler pulleys117.

For the purpose of reinforcing the brackets 61, 62 on the boom housingwith respect to one another and also for the purpose of deflecting anydirt which may be thrown from the chain or digger blades when the chainabruptly changes direction, an arcuate deflector plate 113 is usedmounted on short brackets 119.

To hold the boom down in digging position and to raise the boom uprightfor transport under power when the work is completed, an hydraulicactuator 12% is provided (FIG. 5) having supply lines 121, 122.Connected to the actuator is a rack 123 which operates a gear 124 whichis secured to the hollow stub shaft 66 which forms a part of the boomhousing. Interposed between the rack 123 and the gear 124 is anauxiliary idler pinion 125.

As will be noted, the pinion 125 is on a center which is substantiallyforward of the gear 124 in order to reduce the degree of projection ofthe rack when the actuator is fully extended. The rack and pinion aremaintained in engagement by a back-up roller 126. The source ofhydraulic pressure for powering the actuator 12% will be described at alater point.

It will be apparent from what has been said thus far that the actuator120 serves to rock the boom assembly 30 down into contact with theground. With the digger blades driven by the chain 110 on sprocket 106,the boom gradually cuts its way to an operating position in which it isinclined rearwardly and downwardly from the end of the trencher .andwith the trench being cut upon slow forward movement of the tractionwheels 23, 24.

In accordance with one of the aspects of the present invention, astep-down, high torque drive connection is provided between the engine40 and the traction wheels with means for limiting the transmittedtorque to a predetermined but adjustable value so that forward movementof the trencher is reduced when the blades encounter hard-going, as forexample, when the blades must cut through a thick tree root, with normalforward speed being resumed as soon as a path has been cut through theobstruction. Referring to FIGS. 2, 7 and 8, limitation of torque isaccomplished by an adjunstable hydraulic coupling 131} having an inputshaft 131 and an output sprocket 132. For coupling the input shaft tothe engine, a V-belt 135 is used which is trained about pulleys 136,137, the pulley 136 being directly connected to the crankshaft of theengine. An idler pulley 138 takes up any slack in the belt. From theoutput sprocket 132 of the hydraulic coupling, power is transmitted to atransmission 140 having an input shaft 141 and an output shaft 142. Theconnection is made by a roller chain 145 which is trained over sprockets132, 147 respectively.

Mounted on the output shaft 142 of the transmission, are sprockets 151,152. The sprocket 151 serves to drive the forward traction Wheels 23 bymeans of a sprocket chain 153 and driven sprocket 154, the latter beingpinned to an axle 155 which rigidly interconnects the two front tractionwheels 23. Similarly, the output sprocket 152 drives a chain 157 whichis trained about a sprocket 158 on an axle 159 interconnecting the reartraction wheels 24. A speed reduction of approximately 30:1 is providedin the transmission 140' so that the wheels 23, 24 creep forwardly at aslow trenching speed and with the torque which they exert upon theground being limited in accordance with the value for which thehydraulic coupling has been set.

Referring to the hydraulic coupling 130, the purpose of the device,briefly stated, is to limit the torque transmitted to the tractionwheels to a preset value. It accomplishes this by producing an outputspeed which varies more or less inversely with the torque imposed by theload. Thus, assuming the unit is driven at a constant speed by a primemover, a speed which may in a practical case be 1760 r.p.m., the outputspeed at near zero load may equal the input speed so that there islittle or no slippage. However, as the torque load is increased, theoutput speed drops off or droops until a predetermined equilibrium speedis reached, the actual speed depending upon the setting of the controlelement.

To select a desired speed torque characteristic, the coupling includes acontrol collar 160 (FIG. 8) which is engaged by a lever 161 having oneend pinned to the trencher frame at 162. The other end 163 is connectedto a rod 164 which is connected to a bell crank 165 and which in turn iscoupled to a second rod 166. The latter is operated by a crank 167 towhich is secured the control lever 41 previously referred to. In orderto insure that the control linkage remains in a preset position in spiteof shock and vibration, a friction holding device is provided as shownin detail in FIG. 9. Here it will be noted that the crank 167 is formedon a disc having a conical projection 168 which engages a conical seat169. To draw the surfaces 168, 169 into snug frictional engagement, aspring 170 is used which encircles a bolt 171 which is fixed in positionin the member 167. Consequently, the control lever 41 and the associatedlinkage is securely held in position between adjustments, having a rangeof adjustment all the Way from neutral or zero output to the maximumtorque position limited only by the power of the engine and the strengthof the driven parts.

The present device is not limited to any particular construction ofhydraulic coupling, and adjustable couplings providing a droopingspeed-torque characteristic may be selected by one skilled in the artfrom couplings commercially available. As a guide in selection, FIG. 8ashows characteristics applicable to a practical unit, the curves beingsomewhat idealized for easy understanding. The curves are constanttorque curves, for a range of torque from 4 foot lbs. to foot lbs, withspeed being indicated as a function of the setting of the controlelement 16d. For a given setting, the speed-torque output characteristicis defined by a vertical line, for example, the line 1695:, which showsthat in the face of a change in loading from 4 to 20 foot lbs. the speedvaries from about 1700 rpm. to about 500 rpm. The net eifect is that thetrencher assumes a forward speed in accordance with the load imposed onit, speeding up and slowing down automatically depending upon whetherthe going is easy or hard.

Further in accordance with the invention, the transmission 14fi includesan irreversible worm gear which precludes any retrograde movement of thetraction wheels when the digger blades strike hard clay or the like.Thus, referring to FIG. 10, the input shaft 141 drives a worm 18th whichis in mesh with a worm wheel 181 mounted upon a shaft 182. Since powercannot be transmitted reversely from the worm wheel to the worm, it willbe apparent that retrograde movement of the traction wheels 23, 24cannot occur thereby preventing any tendency toward cyclical reboundunder certain trenching con-,

ditions.

Further in accordance with the invention, means are provided in thetransmission 140 for permitting either forward or reverse rotation ofthe traction wheels at slow speed, thus permitting the transition wheelsto be employed for maneuvering the trencher into position as well as forproviding the necessary tractive effort during digging. In the presentinstance, the reversibility is provided by selectable forward andreverse bevel gears. Referring to FIG. 10, a first bevel gear 19%) isprovided on the shaft 182 running in engagement with forward and reversebevel gears 121, 192. These bevel gears have splines 193, 194,respectively. Centered between them is an output spline 195 which ispinned to the output shaft 142 of the transmission. Slidable endwise onthe splines is a splined collar 196 having a fork 197 and an operatingplunger 198. The latter is coupled to the forward-reverse control 42 bymeans of a linkage 200. Such linkage (FIG. 7) consists of an arm 201which is pinned to the plunger 193, a shaft 202 and an arm 263 connectedto a rod 204. At the upper end of the rod 284 is an arm 265 which isrigidly connected to the control lever 42. It will be apparent then,that by moving the control lever in one direction or the other from itscentral or neutral position, the sliding collar 196 in the transmissionserves to couple the central spline 195 selectively with the splines193, 194 (FIG. 11) to provide the desired forward and reverse rotationof the traction wheels.

In accordance with the present invention, a pair of transport wheels areprovided between the pairs of traction wheels with means for shiftingthem from an upraised idle position to a downwardly thrust position inwhich the transport wheels extend beyond the plane defined by thetraction wheels, and with the transport wheels approximately alined withthe center of gravity when in the lowered position so that the transportwheels may be employed for supporting the trancher either solely orjointly with one of the pairs of traction wheels as the trencher ismaneuvered into working position. In the present instance, the transportwheels indicated at 25 are alined with one another about a transverselyextending axis 210. The wheels are mounted upon cranks 211, 212 securedto a transverse crankshaft 213 which is mounted for rocking movement inthe body of the trencher.

For the purpose of swinging the wheels between their limit positions, a,double-acting hydraulic actuator 215 is provided (FIGS. 11 and 12) whichhas supply lines 216, 217 and which is pivoted to the body of thetrencher at 218. Reciprocable within the actuator is a plunger 219carrying a pin 22%. For coupling the actuator to the crankshaft 213, anoperating crank 221 is provided near the center of the shaft, and havingprovision at its upper end for receiving the pin 220 on the plunger.

In accordance with one of the aspects of the present invention, a latchor detent is provided for the operating crank 221 for positively lockingthe transport wheels in their downwardly thrust position at the end ofthe stroke of the actuator and with provision for releasing the latchwhen the actuator is subsequently moved in the opposite direction. Inthe present instance the pin 220 serves as the latch member riding in aslot 222 and cooperating with an abutment 225 on the trancher body whichis arranged in the path of movement of the pin. For guiding andreceiving the pin the abutment member 225 includes a notch 226 having anadjacent ramp 227.

To understand the operation of the locking arrangement, considerationmay be given to a cycle in which the transport wheels are lowered fromthe upraised position shown in FIG. 11 to the operating position shownin FIG. 12. Hydraulic fluid is supplied to the actuator 215 through theline 216 causing the plunger 219 to be drawn upwardly. Such movement isaccompanied by clockwise rotation of the crank 221 accompanied byswinging of the transport wheels 25 in the downward direction. As theplunger 219 nears the end of its stroke, interference takes placebetween the pin 220 and the ramp 227 causing the pin to be cammeddownwardly in the slot 222 formed in the crank. As the pin 220 ridesalong the ramp, a point of drop-off is reached following which the pinmoves into the notch 226 so that the plunger is free to take up the lostmotion between the crank 221 and the pin. This seats the pin 220 fullyin the slot 226 thereby locking the crank 221 and the transport wheelsin the position shown in FIG. 12. It will be noted that such lockingdoes not depend upon the existence of any pressure in the actuator 215.Thus, ground reaction on the transport wheels tends to rotate the shaft213 to which they are secured in a counterclockwise direction. However,because of the interference between the pin 220 and the wall of thenotch 226, no rocking movement can take place. Consequently, thetransport wheels are fixed in position and there is no risk that thetraction wheels will be lowered into contact with the ground eitherduring maneuvering or long-distance hauling.

When pressure is re-applied in the opposite direction, automaticunlocking of the pin 220 occurs incident to the taking up of the lostmotion between the plunger and the crank. Thus, referring to FIG. 12, itwill be apparent that downward thrusting movement of the plunger 219acts first to move the pin 220 out of the notch 226. Continued thrustcauses the freed pin 22% to ride along the ramp 227 accompanied bycounterclockwise rotation of the crank 221 and upward swinging of thetransport wheels 25 on their respective crank arms. This restores thetransport wheels to the out-of-the-way position shown in FIG. 11, andthe weight of the trencher is fully restored to the traction wheels 23,24.

In order to understand the hydraulic system employed powering theactuator 215 which raises and lowers the transport wheels and theactuator 120 which raises and lowers the boom, reference is made to FIG.13. Fluid pressure is derived from a pump 230 having an output orpressure line 231 and a return line 232 feeding a sump 233. To controlthe admission of pressure fluid alternatively to the lines 121, 122supplying the boom housing actuator, a first valve 235 is providedconnected to the boom control lever 43. Moving the control lever 43 tothe left as shown in FIG. 13 causes fluid pressure to be applied to theline 121 to raise the boom while movement of the control lever 43 in theopposite direction applies pressure to the line 122 to lower the boom.Similarly, an hydraulic valve 236 is associated with the hydrauliccontrol lever 44 so that movement of the lever in one direction causespressure to be supplied to the line 217 expanding the actuator andswinging the wheels into the up position, whereas moving the controllever in the opposite direction applies pressure to the line 216retracting the plunger 219 so that the transport wheels are thrustdownwardly into the ground-engaging position. All of the control leversare, as noted in FIG. 1, within easy reach of the hands of the operator.

In accordance with one of the features of the present invention, one ofthe pairs of traction wheels is spaced more closely together than theother and is mounted in a recessed or nested position within theconfines of the transport wheels. Thus, as shown in the drawings andparticularly FIGS. 2 and 4, the rear traction wheels 24 are closelyspaced inside of the trencher body and re cessed within the transportwheels 25. Prior to discussing the advantages which result from thisarrangement, it will be helpful at this point to point out a stillfurther feature of the present construction. Thus, in carrying out theinvention, the body 21 is made of hollow box-like construction includinga pair of spaced hollow protuberances which not only accommodate theboom assembly bet-ween them but which provide housing and support forthe narrowly spaced traction wheels 24. In the present instance, the twoprotuberances are indicated at 241, 242, respectively, defining a space243 between them which is sufficiently wide to accommodate the brackets61, 62 at the inner end of the boom housing. Moreover, the inner opposedwalls of the protuberances, indicated at 245, 246, serve to mount theboom housing bearings 67, 68, previously referred to. Finally, it is afeature of the present invention that the rounded tip portions of theprotuberances indicated at 247, 248 are separable from the body along aline 249 and serve as a mounting for the mating parts of the twobearings 67, 68. In short, the members 247, 248 serve the function ofbearing caps and, when removed, provide access to the interior of thebody of the trencher as shown in FIG. 4.

The primary advantage of the nested traction wheel construction is thatthe over-all length of the trencher body is substantially reducedproducing a design which has great inherent compactness. The resultingshort wheel base makes the machine more easily maneuverable and moreeasily transported from place to place. The compactness is indeedstriking when it is considered that the trencher has six full-sizedwheels, with the appearance more closely resembling that of a fourwheeled vehicle. Moreover, the traction wheels 24 are out of the path ofmovement of the transport wheels 25 as the latter are swung on theircranks between their raised and lowered positions thereby permitting alarge range of vertical movement for the transport wheels free of anyclearance limitations. Also important is the fact that each of the fourtraction wheels follows a separate track and therefore each can secure afresh positive grip upon the ground which is desirable under slick,clayey conditions.

It is an over-all feature of the present construction that the trenchermay be maneuvered, either manually or with power, by a single operatorto desired operating position even in close quarters where aconventional jeep or tractor-mounted trencher cannot be used. Thus,referring to FIG. 14, since the transport wheels are alined with thecenter of gravity, it is an easy matter for the operator to balance thetrencher above the transport wheels and the trencher may, if desired, besimply wheeled into position. When supported on the two transportwheels, which are independently rotatable, the entire trencher may, withextremely light manual force, be turned or skewed in order to achievethe desired alinement with the direction of cut. Where it is desiredduring the maneuvering operation, to drive the trencher in one directionor the other with power from the engine, it is sufiicient for theoperator to rock the trencher downwardly about the transport wheels,thereby bringing one set of the traction wheels 23, 24 into engagementwith the ground. With the torque control handle set in the lower portionof its range, the forward-reverse lever 42 may then be moved in onedirection or the other to drive the trencher at a slow speed, eitherforwardly or backwardly. If desired, the traction wheels may be leftrunning at a slow speed While the trencher is balanced on the transportwheels and the unit may be rocked so that one set of the transportwheels, preferably the forward set, comes into grazing contact with theground. This gives the operator precise control of the amount of drivingeffect without requiring the operator to adjust the control levers.Thus, the operator has a delicate control of speed without having tomove his hands from the handles 51, 52.

In short, it has been found that a trencher constructed as describedabove may be maneuvered into any desired working position quickly andwith minimum effort by a single operator in spite of the fact that themachine may have a total weight on the order of 1100 pounds. Completeflexibility is provided by applying a combination of light rocking andskewing movements to the guiding handles, a knack quickly acquired by anoperator. This is to be contrasted with conventional manually directedtrenchers which are either so light as to be ineffective in digging atrench of useful size, or so heavy and unbalanced as to be awkward tomaneuver, requiring the services of several men to wrestle the trencherinto position. The trencher is also to be contrasted with units whichrequire the wheels to be unpinned for maneuvering purposes.

The present trencher is particularly suited for drawing at high speedbehind an automobile or truck from one job to another as shown in FIG.15, with the hitch 55 at the front end of the trencher being securablein the usual fashion to the ball of a conventional bumper hitch. Totransport the trencher from the job, the transport wheels are loweredinto ground-engaging position where auto matic locking takes place ashas been previously discussed in connection with FIG. 12. The engine maythen be turned ofi since the transport wheels are locked even withoutpressure in the associated actuator 215. The front end of the hitch 55is then secured to the ball and a canvas cover may be used, as indicatedin FIG. 15, to protect the engine of the trencher from the dirt ormoisture which may be thrown up from the road.

In accordance with one of the detailed aspects of the invention, meansare provided for varying the height of the hitch connection 55 so thatthe height of the traction wheels on the trencher may have the sameground clearance independently of the height of the ball on the towingvehicle. To accomplish this, a novel hitch arrangement is used having aheight-adjusting mechanism generally indicated at 250 (FIG. 16). Thehitch is secured to an extensible tongue 251 which is slidable in anangularly adjustable socket 252. The tongue is maintained in a desiredextended position with respect to the socket by a bolt 253. In carryingout the invention, the socket 252 is pivoted to the body of the trencherfor rocking about a horizontal pin 254 and means are provided forholding the socket in predetermined angular position. In the presentinstance, this is accomplished by providing the 11" socket 252 with apair of spaced downward extensions 255 (only one being shown) having anut 256 between them. The nut is engaged by an adjusting screw 257received in the apron 258 of the trencher body. Lock nuts 259, jammedtogether, serve as a thrust collar to keep the screw 257 seated in theapron 258. Thus, for maximum ball height, the adjusting screw 257 may bescrewed as far as possible into the nut 256, causing the socket 252 toassume the upwardly angled position illustrated in FIG. 16. In order touse the bitch with a lower ball, the adjusting screw 257 is turned torock the socket 252 counterclockwise into the position shown dotdash.Any play between the parts is taken up by a clamping mechanism 260. Thismechanism includes a rockable clamping member 261 which is pivoted tothe pin 254 and which has a cam surface 262. The lower end of the member261 is engaged by a threaded thumb screw 263. It will be apparent thatregardless of the angling of the socket member 252, screwing the thumbscrew 263 inwardly causes the clamping member 261 to be cammed againstthe tongue 251 thereby taking up the looseness or play between thetongue and the socket or between the socket and the body of thetrencher.

It will be apparent that by use of the novel hitch arrangement, thehitch 55 may be moved upwardly or downwardly as may be necessary toequalize the clearance of the traction wheels and the trencher maytherefore be pulled by diflerent automobiles or trucks, as may beconvenient. With maximum ground clearance assured, and with automotivetype bearings in the wheels 25, the present trencher may be pulled athigh speed along a highway so that the time lost between jobs may bereduced to a minimum. Moreover, a single trencher of the above type maybe used by a single contractor to cover a wide area of operation, muchwider than might be covered, for example, by a tractor-mounted trencher.Because the trencher is substantially balanced over the transportwheels, a light vertical hitch force is assured. The expense of atrailer or dolly is saved.

Not only is the trencher easily maneuvered or jockeyed into position,but it tends to follow a straight line with minimum effort on the partof the operator. Where the trencher strikes a patch of hard packed clay,a thick tree root or similar obstruction, the limitation of the torqueto the traction wheels, and the drooping speed characteristic of thehydraulic coupling, causes the trencher to be slowed down automaticallyuntil the digger blades have had opportunity to cut their way throughthe obstruction, whereupon normal forward speed is resumed, all withoutcare or attention on the part of the operator. All of the controls arereadily accessible at the front end of the machine so safe, convenientcontrol is assured. Moreover, because of the irreversible nature of thedrive, retrograde action of the traction wheels is prevented and therebound experienced particularly in light weight trenchers under certaindigging conditions is minimized, with the trencher proceeding on asmooth steady course. The trencher in spite of its small size is capableof digging trenches of considerable width and of a depth whichapproaches that achieved by trenchers mounted on a tractor or jeep.Consequently, the trencher may be employed for all but the very heaviestwork.

The trencher body being of box-like construction, is extremely rigid forits weight. The length of which the body is made may be accuratelyjig-welded and parts may be fitted into the body with an alinementaccuracy which greatly exceeds the accuracy attainable in conventionaltrencher construction. Instead of having tolerances characteristic offarm implements, fits and alinements are established with high precisionenabling the unit to with stand hard useage over a long period of timewithout adjustment and with only causal maintenance, primarilylubrication. In this connection, the transport wheels serve as abuilt-in jac which greatly facilitates inspection and servicing. Thus,when the transport wheels are 12 shifted to their lowermost position,the trencher may be rocked fully in one direction or the other to bringeither pair of traction wheels into contact with the ground, thusexposing for view and easy access approximately one-half of theunderside of the machine. The trencher will remain stable in eitherposition.

While the invention has been described above in connection with apreferred embodiment, it will be understood that an alternate mode ofoperation may be secured by the making of a minor change in thetransmission and which is accompanied by a number of novel advantages.Thus, it is contemplated that as part of the present invention, meansmay be provided for causing the two pairs of traction wheels to rotatesimultaneously but in opposite directions when the trencher is balancedon the transport wheels and while it is being maneuvered into position,thereby permitting the trencher to be propelled slowly in one directionor the other simply by lowering the appropriate pair of traction wheelsinto grazing contact with the ground without requiring the shifting ofany forward-reverse lever in order to achieve the two directions ofmotion. In the present instance, this is brought about by modifying thetransmission 140 as set forth in FIG. 17, where corresponding referencenumerals indicate elements corresponding to those in FIG. 10. Here itwill be noted that the shaft 142 which is connected to the outputsprockets 151 and 152 has been split into two parts, 271, 272. Outputsprocket 152a, which is connected to the rear traction wheels, iscoupled directly to the bevel gear 192a by shaft 271 as indicated by thepin 273. Output sprocket 151a, which is coupled to the front tractionwheels is coupled to the central spline 195a by a pin 274. Thus, whenthe shiftable splined collar 196a is in the righthand position as viewedin FIG. 17, the output sprocket 15112 is connected directly to theoutput sprocket 152a for rotation of all four of the traction wheels inthe same direction as required for normal trenching.

However, when the splined collar 195a is moved to its opposite orleft-hand position, then the central spline 195a is directly coupled tothe spline 1930 on the opposite bevel gear 1910:. Since the bevel gear191a always rotates in the opposite direction from the bevel gear 192a,such shift causes the output sprocket 151a to rotate the forwardtraction wheels in the opposite direction. Thus, under such conditionsthe two pairs of traction wheels will rotate simultaneously but inopposite directions. Operation under such conditions may be clearlyvisualized with reference to FIG. 14. Thus, upward pressure applied tothe manual guiding handles serves to rock the trencher in a clockwisedirection about the transport wheels so that the traction wheels 24 arebrought into grazing contact with the ground propelling the trencher inthe same direction that the operator is facing. At any time the operatorcan ease off on such driving movement by rocking the trencher back intoits balanced position. Conversely, the operator may apply downwardpressure upon the guiding handles which will bring the traction wheels23 into grazing contact with the ground, causing the trencher to bepropelled toward the operator. Again, movement in such direction may beterminated simply by rocking the trencher back to its centeredcondition. Thus, by a combination of rocking movements in one directionor the other under relatively light manual pressure, the trencher may bejockeyed forwardly and backwardly. This combined with the skewingmovement already referred to in which the trencher is skewed sideways inone direction or the other to change its direction of movement, enablesthe trencher to be positioned in precise operating position in a minimumof time.

While the latter mode of operation has the advantage of flexibility andenables maneuvering under power in both directions without requiring thecontrol levers to be touched, nevertheless, this mode of operation doesrequire slightly greater care and skill for full utilization, and forthis reason, the earlier mode of operation will normally treatise bepreferred. The position of the control lever 42 which makes the twodirections of movement simultaneously available to the operator may bedesignated Fwd-Rev. (forward-reverse), while the opposite position usedin actual trenching may be designated simply Fwd. While the transmissionmodified in accordance with FIG. 17 does not provide a central neutralsetting in which both sets of traction wheels are turned completely off,this ofi position can nevertheless be achieved simply by moving thecontrol lever 41 to its off or neutral position at one end of thecontrol range.

In the following claims, the term shifting as applied to the transportwheels shall be understood to mean shifting relative to the tractionwheels since it will be apparent to one skilled in the art that theinvention is not limited to movement of the transport wheels but isbroad enough to encompass corresponding relative movement of thetraction wheels between upraised and ground-engaging positions.

We claim as our invention:

1. In a trencher the combination comprising a frame, digger meansincluding movable digger blades, on said frame, a prime mover having adrive connection to said digger blades, a first pair of traction wheelsat one end of the frame rigidly coupled together, a second pair oftraction wheels at the other end of the frame rigidly coupled together,a pair of individually rotatable transport wheels between said pairs oftraction wheels, said transport wheels having substantially the samespan as the first pair of traction wheels, and said second pair oftraction wheels having a substantially reduced span and being nestedwithin the confines of transport wheels so that the second set oftraction wheels is overlapped by the transport wheels, and means forraising and lowering the traction wheels with respect to the bodybetween limit positions.

2. In a trencher the combination comprising a body, a digging boomhaving movable digging blades and mounted at one end of the body, aprime mover on said body having means for driving the blades, fore andaft pairs of traction wheels rotatably mounted on said body for normallysupporting the same, a pair of transport wheels mounted on said bodyalong a transverse axis generally alined with the center of gravity ofthe trencher and having means for vertically shifting the same into alowered position beyond the plane of normal support and so that at leastone pair of the traction wheels is upraised from the ground, a slowspeed high torque driving connection interposed between the prime moverand the traction wheels, said driving connection having manuallyadjustable means for limiting the transmitted torque to a predeterminedvalue, said torque limiting means having a drooping speed characteristicso that when the digger blades strike a root or similar obstruction thespeed of the traction is automatically slowed while maintaining thenormal speed of the digger blades until such obstruction is overcome.

3. In a trencher the combination comprising a body, a digging boomhaving movable digging blades and mounted at one end of the body, aprime mover on said body having means for driving the blades, fore andaft pairs of traction wheels rotatably mounted on said body for normallysupporting the same, a pair of transport wheels mounted on said bodyalong a transverse axis generally alined with the center of gravity ofthe trencher and having means for shifting the same into a loweredposition beyond the plane of normal support and so that at least onepair of the traction wheels is upraised from the ground, a slow speedhigh torque driving connection interposed between the prime movement andthe traction wheels, said driving connection having manually adjustablemeans for limiting the transmitted torque to a predetermined value,axial driving connection including non-retrograde worm gearinginterposed between the torque limiting means and the traction wheels.

4. In a trencher the combination comprising a body of generally boxshape terminating at one end in a pair of hollow box-like protrusionsdefining a vertical opening between them, a digging boom having one endarranged in said vertical opening and journaled in said protrusions topermit vertical swinging movement of the boom, said boom having a seriesof movable digger blades, a prime mover in said body coupled to thedigger blades, a first pair of traction wheels mounted outboard of thebody at the end thereof opposite the digging boom, a second pair oftraction wheels recessed in said protrusions and generally under thepoint of pivoting of said boom, a slow speed high torque drivingconnection for coupling the prime mover to the traction wheels forcreeping movement of the trencher with the blades in digging engagementwith the ground, handles on said body at the end opposite said boom formanually guiding the trencher, a pair of transport Wheels outboard ofsaid trencher body and mounted on an axis intermediate the axes of thetraction wheels, and means for shifting said transport Wheels downwardlyfor supporting the trencher with the traction wheels elevated above theground.

5. In a trencher the combination comprising a body of generally boxshape terminating at one end in a pair of hollow box-like protrusionsdefining a vertical opening between them, a digging boom having one endarranged in said opening and journaled in said protrusions to permitvertical swinging movement of the boom, said boom having a series ofmovable digging blades, a prime mover in said body coupled to the diggerblades, a first pair of traction wheels mounted outboard of the body atthe end thereof opposite the digging boom, a second pair of tractionwheels recessed in said protrusions and generally under the point ofpivoting of said boom, a sloW speed high torque driving connection forcoupling the prime mover to the traction wheels for creeping movement ofthe trencher with the blades in digging engagement with the ground, apair of transport wheels outboard of said trencher body and partiallyoverlapping the wheels in said protrusions, and means for shifting saidtransport wheels downwardly beyond the traction wheels.

6. In a trencher the combination comprising a body of generally boxshape having at one end a pair of hollow box-like protrusions defining avertical opening between them, a digging boom having one end arranged insaid opening and having laterally extending trunnions, bearings in saidprotrusions journalling said trunnions to permit vertical swingingmovement of the boom, said boom having a series of movable diggerblades, a prime mover in said body having means for driving the diggerblades, a first pair of traction wheels mounted outboard of the body atthe end thereof opposite the digging boom, a second pair of tractionwheels recessed in said protrusions and generally under the point ofpivoting of said boom, a slow speed high torque driving connection forcoupling the prime mover to the traction wheels for creeping movement ofthe trencher with the blades in digging engagement with the ground, theends of said protrusions being separable from the body to serve asbearing caps and upon removal to permit access to the interior of saidprotrusions.

7. In a trencher the combination comprising a body of generally boxshape having at one end a pair of hollow box-like protrusions defining avertical opening between them, a digging boom having one end arranged insaid opening and journaled between said protrusions to permit verticalswinging movement of the boom, said boom having a series of movabledigger blades, a prime mover in said body having means for driving thedigger blades, a first pair of traction wheels mounted outboard of thebody at the end thereof opposite the digging boom, a second pair oftraction wheels recessed in said protrusions, a slow speed high torquedriving connection for coupling the prime mover to the traction wheelsfor creeping movement of the trencher with the blades in engagement withthe ground, and a pair of independently 15 rotatable transport wheelsoutboard of said trencher body having means for vertically shifting thesame into lowered transport position.

8. In a trencher the combination comprising a body of hollow box shape,a digging boom having movable digger blades and mounted on said body, aprime mover on said body having means for driving the blades on thedigging boom, a first pair of traction wheels mounted outside of thebody, a second pair of traction wheels mounted inside of the body spacedfrom the first pair, a slow speed high torque driving connection forcoupling the prime mover to the traction wheels, a pair of transportwheels mounted outside of the body between the traction wheels and at aposition approximately alined with the center of gravity of thetrencher, and means for locking the transport wheels in a lowered,trencher supporting position permitting the trencher to be maneuveredwhile totally supported on the transport Wheels.

9. In a trencher, the combination comprising a body, a digging boomhaving movable digger blades and mounted for vertical rocking movementat the rear end of said body, a prime mover on said body having meansfor driving the blades on the digging boom," fore and aft pairs oftraction wheels on said body for supporting the same during operation ofthe digger blades, a slow speed high torque driving connection forcoupling the prime mover to the traction wheels, a pair of transportwheels rotatably mounted on said body along a transverse axisintermediate the pairs of traction wheels, said transport wheels havingmeans for positioning the same with respect to the body so that theyproject beyond the support plane defined by the traction wheels, a towbar at the front end of the body and having a hitch connection forsecuring the front end of the tow bar to a tractive vehicle fortransport from job to job, and means for vertically adjusting theelevation of the hitch with respect to the body of the trencher so as toprovide substantially equal clearance for the traction wheels underconditions of transport regardless of the elevation of the hitch pointon the vehicle.

10. In a trencher the combination comprising a body, a digging boomhaving movable digger blades and mounted for vertical rocking movementat the rear end of said body, a prime mover on said body having meansfor driving the blades on the digging boom, fore and aft pairs oftraction wheels on said body for supporting the same during operation ofthe digger blades, a slow speed high torque driving connection forcoupling the prime mover to the traction wheels, a pair of transportwheels rotatably mounted on said body along a transverse axisintermediate the pairs of traction wheels, said transport wheels havingmeans for positioning the same with respect to the body so that theyproject beyond the support plane defined by the traction wheels forsupporting the trencher during maneuvering and transport, handles at thefront end of the body for manually guiding the trencher, a tow bar atthe front end of the body and having a hitch connection for securing thefront end of the tow bar to a tractive vehicle for transport from job tojob, and means for telescoping the tow bar into an out-of-the-wayposition in said body during manual guidance of the trencher.

11. In a trencher the combination comprising a body, digging meansincluding a boom and a digger chain on said body, a prime mover on saidbody having means for coupling the same to the digger chain, fore andaft pairs of traction wheels journaled in the body, a slow speed driveconnection between the prime mover and the traction wheels, a pair ofauxiliary transport wheels located on an axis between the tractionwheels and vertically movable between an upraised position in which thetraction wheels are clear of the ground and a lowered position in whichthe transport wheels are below the level of the traction wheels fortotal support of the frame for transport, means for mounting thetransport wheels for vertical movement relative to the traction wheels,means including a double acting hydraulic actuator coupled to themounting means for moving the same between limit positions, and lockingmeans automatically engageable incident to the movement of the transportwheels into their lowered trencher supporting position so that thetransport wheels are maintained in such lowered position independentlyof subsequent lack of pressure in the hydraulic actuator.

12. In a trencher the combination comprising a body, digging meansincluding a boom and a digger chain on said body, a prime mover on saidbody having means for coupling the same to the digger chain, fore andaft pairs of traction wheels having respective shafts journaled in thebody, a slow speed drive connection between the prime mover and theshafts of the traction Wheels, a pair of auxiliary transport wheelslocated on an axis between the traction wheels, a shaft cranked at itsends for mounting the transport wheels on the body, an operating crankon said shaft, pinned to the operating crank to move the transportwheels vertically between an upraised position in which the tractionwheels are clear of the ground and a lowered position in which thetransport wheels are below the level of the traction wheels for totalsupport of the trencher for transport, a lost motion connection betweenthe activator and operating crank, and locking means automaticallyengageable incident to the taking up of the lost motion following theswinging of the transport wheels into their lowered position so that thetransport wheels are maintained in lowered trencher supporting positionindependently of subsequent lack of pressure in the hydraulic actuator.

13. In a trencher the combination comprising a body, digging meansincluding a boom and a digger chain on said body, a prime mover on saidbody having means for coupling the same to the digger chain, fore andaft pairs of traction wheels journaled in the body, a slow speed driveconnection between the prime mover and the traction wheels, a pair ofauxiliary transport wheels located on an axis between the tractionwheels, means including a crank for mounting said transport wheels onthe body for movement downwardly beyond the traction wheels as the crankis swung to the end of its range of movement, a double acting hydraulicactuator pinned to the crank and having a limited amount of radial lostmotion with respect to the latter, and an abutment on the body sopositioned as to obstruct arcuate movement of the crank incident to theactuators taking up the lost motion so that the transport wheels aremaintained in lowered frame supporting position independently of lack ofpressure in the hydraulic actuator and so that subsequent movement ofthe actuator in the opposite direction is effective to free the crankfrom this abutment.

14. In a trencher, the combination comprising a body, a digging boom onsaid body and having movable digger blades, a prime mover on said bodyhaving means for driving the blades, fore and aft pairs of tractionwheels on said body spaced from one another to provide stable supportfor the body, a step-down driving connection interposed between theprime mover and the pairs of traction wheels for normally driving thewheels in the same direction for slow advancement of the digging boom inthe ground, handles on the body remote from the digging boom formanually guiding the trencher, a pair of transport wheels locatedintermediate the pairs of traction Wheels and having means for shiftingthe same between an upraised position clear of the ground and a loweredposition below the level of the traction wheels and in which the vehiclemay be balanced solely on the transport wheels, the transport wheelsbeing independently pivoted to permit skewing of the trencher in onedirection or the other, and means for reversing the slow speed driveconnection to one of the pairs of traction wheels for causing the pairsof traction wheels to rotate in opposite directions so that the operatorsimply by tilting the body forwardly or backwardly about the transportwheels 17 18 may bring a selected pair of the traction wheels into2,777,2 19 Brant Jan. 15, 1957 grazing contact with the ground tomaneuver the trencher 2,828,557 Brown Apr. 1, 1958 forwardly andbackwardly into a desired position.

FOREIGN PATENTS References Cited in the file of this patent 5 573 251Great Britain June 4 1952 UNITED STATES PATENTS OTHER g g ggg 1,722,5351Matter Jul 30, 1929 L 2,748,504 McIm-nch g 5, 1956 C1v1l Engmeenng, July1957, vol. 27, No. 7, Model 2,751,698 Brown June 26, 1956 M Ditch-WitchTrencher, pages 124 and 125 relied on.

